Introduction

The last sixty days prior to calving has the potential to be a challenging time for first calf heifers. The primiparous cow must successfully adapt to numerous physiological and behavioral changes related to calving and the initiation of lactation. Primiparous cows must adapt to changes in housing, feeding, management, and to milking. Strategies that reduce stress around the time of calving should optimize the chance for success. Additional challenges include appropriately comingling multiparous and primiparous cows to minimize negative social interactions. Our goal for a successful primiparous heifer program should be to reduce the number of metabolic, psychological, and pathogenic hurdles during the transition period. Calving and initiation of lactation are two unavoidable hurdles. Our focus should be to tear down additional hurdles through adaptive nutrition and behavioral management prior to calving. According to the USDA national animal health monitoring survey (2007), 36.2 of herds surveyed consist of first-calf heifers. Primiparous heifers represent the present and the future of dairy farms.

A large (n = 1905) heifer field study was conducted in California to evaluate the effects of age at first calving (AFC) on postpartum performance and health (Ettema and Santos, 2004). Culling after calving and mortality in this study was similar among AFC and averaged 17.6% and 3.9% respectively. Incidence of mastitis averaged 19.4% among the groups of heifers, cases of lameness averaged 15%, and left displaced abomasums averaged 2.9%. Even on well managed herds, opportunities for improvement exist.

Deviations from the normal population must be identified and addressed. Identifying the cause and determining the solutions of challenges that cause health problems, increase premature culling and hinder the ability to perform should be a high priority in all dairy herds.

Transitioning primiparous cows often receive less attention than second and greater lactation cows. Perhaps primiparous cows have a lowered status on the priority list due to seemingly lower health problems such as milk fever and displaced abomasum during the transition period when compared to their older counterparts. Fresh primiparous cows have a greater prevalence of mastitis than older cows, despite lower reported incidence of mastitis later in lactation (Miltenburg et al., 1996; Barkema et al., 1998; Nyman et al., 2007). This increased incidence in mastitis in primiparous cows may indicate they are less able to cope with stressors during the periparturient period.

Improvements in transition programs for primiparous cows will have an effect on herd performance today and in subsequent lactations. Investigating strategies to promote favorable energy balance, reduce negative social and behavioral interactions, reduce health challenges, and increase milk production may improve the profitability of primiparous cows.

Energy intake

Often primiparous cows are moved from the heifer grower and placed into the far-off dry cow group 60 days prior to calving. The objective of this pen movement is to adapt first calf heifers to new surroundings, expose them to social interactions with older cows, and to feed an appropriate diet. Moderate energy or controlled energy diets are diets based on wheat straw and silage that are offered at an ad libitum rate, but do not allow cows to greatly over-consume energy (Beever et al., 2006; Dann et al., 2006; Janovick-Guretzky et al., 2006). Moderate energy diets for mature dry cows have been implemented with success and are being adopted by producers. Are moderate energy diets appropriate for first primiparous cows? Primiparous cows exhibit negative energy balance in early lactation similar to that of multiparous cows (Lin et al., 1984). Primiparous cow's produces less milk compared to multiparous cows, but may be at risk for similar severity of negative energy balance after calving (Cavestany et al., 2005; Wathes et al., 2007).

Metabolic differences between primiparous and multiparous cows prepartum are numerous. Primiparous cows have not yet reached mature body weight so changes associated with growth place demands on anabolic pathways. Primiparous cow's investment in colostrum quantity and quality and milk yield is typically less than that of a mature cow.

Differences in metabolic traits, milk yield, and body condition score between primiparous and multiparous cows during the periparturient period were investigated by workers in Great Britton (Wathes et al., 2007). Data from Wathes et al. (2007) indicated that primiparous cows had higher concentrations of insulin-like growth factor-1 and lower ß-hydroxybutyrate (BHBA) concentrations one week before and seven weeks after calving, higher leptin pre-partum, and both the peak in non-esterified fatty acids (NEFA) and the nadir in urea concentration occurred earlier after calving compared with multiparous cows. These authors concluded that there are differences in the regulation of metabolism between primiparous and multiparous cows that promote nutrient partitioning into growth as well as milk during the first lactation (Wathes et al., 2007). Twenty Swedish herds participated in a study to evaluate changes in metabolites and immune variables associated with somatic cell counts in primiparous cows (Nyman et al., 2008). Results from this large study showed that greater concentration of BHBA and glucose before calving were associated with reduced Box-Cox transformed somatic cell counts (bcSCC) at first test milk sampling. However, greater concentrations of NEFA before calving and greater change in NEFA at calving were associated with greater bcSCC at first test-milking.

Protein intake

Adjustments are often made to increase the dietary protein content of the diet when multiparous cows and first calf heifers are mixed to meet the higher protein requirement for growth. Santos et al., 2001 suggested that primigravid cows might benefit from diets with crude protein content greater than 12.7%. Primiparous cows were fed one of two diets containing a moderate amount of crude protein (12.7%) or a higher crude protein amount (14.7%). Primiparous cows fed the prepartum diet higher in protein produced 2.0 kg/d more milk and 3.1 kg/d more 3.5% fat corrected milk during the first 120 days in milk. In the first month after calving, Nyman, et al. (2009) associated low milk urea nitrogen (MUN) (< 4 mmol/L) with elevated somatic cell count at first test day in primiparous cows. Low MUN indicates insufficient dietary protein (Ipharraguerre et al., 2005; Schei et al., 2005).

Age at first calving

Age at first calving (AFC) is an important factor in the cost or rearing replacements in dairy herds. Optimal AFC in Holsteins was recommended to be < 24 mo with body weight > 560 kg after calving at 24 mo (Heinrichs, 1993; Tozer and Heinrichs, 2001). Age at first calving has been shown to have an impact on health in primiparous cows. Waage et al. 1998) observed an increased risk of mastitis with increased age at first calving. A similar association between age at calving and ketosis was also observed (van Dam et al, 1988). Swedish and Danish researchers hypothesized that metabolites and immune variables may differ between primiparous cows ad different age at first calving (Nyman et al., 2008). Primiparous cows calving at >27 mo of age had greater BHBA and NEFA values, and lower glucose, insulin, and urea nitrogen compared with heifers calving at <27 months (Nyman et al., 2008). Heifers calving at an age <25 mo had greater conglutinin (collectin involved in pathogen recognition) and urea nitrogen values and lower NEFA compared with heifers calving at >25 mo (Nyman et al., 2008).

Should primiparous cows be fed anionic salts?

The default diet for primiparous cows during the dry period is often whatever the multiparous dry cows are being fed. Housing primiparous and multiparous dry cows together creates a challenge for nutritionists attempting to modify the dietary cation-anion difference (DCAD) with anionic salts. Anionic salts are used to decrease the DCAD to aid in prevention of hypocalcemia through increasing calcium mobilization from bone and increased uptake of calcium from the intestine. Primiparous cows at calving are typically 80-85 percent of their mature body weight, so bone growth and remodeling is still occurring, making bone calcium more readily available.

Researchers at Michigan State fed multiparous and primiparous cow's prepartum diets containing anionic salts to achieve DCAD's of +15, 0, and -15 meq/100g. Prepartum dry matter intake, energy balance, and body weight gains were lower and concentration of liver triglyceride was higher for heifers but not cows fed the -15 DCAD diet (Moore et al., 2000). The authors concluded that heifers should not be fed anionic salts before calving as they maintained calcium homeostasis through the transition period regardless of dietary DCAD, but consumed less DM when fed the -15 DCAD (Moore et al., 2000).

Behavioral adaptations

In addition to the physiological and metabolic changes associated with calving and the initiation of lactation, primiparous cows must adapt to comingling with older, socially dominant cows, learn to use head locks and freestalls, become accustomed to increased handling by humans, and adjust to the milking routine. Separate feeding and management of primiparous and multiparous cows is warranted (Grant 2007; Daniels et al., 2008), but is often not practical especially on smaller herds.

According to the NRC (2001) primiparous cows consume less feed and in a different pattern (peaking later) than multiparous cows. Additionally, it is believed that primiparous cows are usually more timid and occupy a lower rank in the social herd hierarchy (Wierenga, 1990). Interesting data from Spain showed total eating time was longer when primiparous cows were housed with multiparous cows, however, primiparous cows housed alone had almost 1 more meal per day than did those housed with multiparous cows (Bach et al., 2006). Feeding area was limited to one feeder per 1.8 cows; however, more than 50% of the feeders at time of feeding were occupied by primiparous cows, suggesting they were not intimidated by multiparous cows (Bach et al., 2006). Housing multiparous and primiparous cows together may offer advantages in exposing heifers to intensified competition prior to calving as well as assumption of learned behaviors.

Two producers in the upper Midwest that I recently visited with have interesting philosophies on feeding behavior in close-up heifers and cows. One producer purposefully overcrowds the close-up group to increase competition at the feed bunk and purportedly stimulate intake. Data published by Bach et al. (2006) seems to support this theory although results might not be the same in all situations. Another producer on a large dairy constantly mixes pens of dry cows to reduce the groups desire to develop a strong social hierarchy. The mixing of dry cow pens seemingly reduces negative social interactions and helps fresh cows acclimate to herd mates in the fresh cow pen.

Smooth return from the heifer grower

Whether heifers are raised by the owner or farmed out to a heifer grower, a smooth transition into the milking herd is important to the success of the first and subsequent lactations. Variables such as avoiding overconditioning, calving at an appropriate age, and experience with the use of headlocks and free-stalls are important factors that will impact transition success of first calf heifers. The amount of time before expected calving date heifers are returned to the milking herd may have some impact on transition success.

In the most recent NAHMS survey (2007), heifers returning to the milking herd from the heifer grower averaged 21.6 months of age (USDA, 2007). Heifers are typically brought back to the milking herd as early as 3 months or as late as 3 weeks prior to expected calving date. Synchronization programs have helped in producing larger groups of heifers with similar calving dates. Increased variability in calving date occurs when a heifer with a calving date that is an extreme outlier from the mean or one with an incorrect expected calving date steps foot on the truck.

Scheduling of heifer pickup may be a factor contributing variability in the primiparous heifer transition program. Clearly the truck does not run every day to pick up heifers so the arrival time at the milking herd is a potential source of variability. Adequate time should be allowed for all heifers to adapt to their new surroundings and to minimize the negative impact on those that calve earlier than expected. Clearly constraints in facility capacity, labor, and management must be evaluated to determine the optimal timing of heifer return from the grower.

USDA survey data indicates that small and medium operations sending heifers off-site to be raised were transported fewer than 20 miles while large herds transported heifers between 5 and 50 miles (USDA, NAHMS 2007). Of all operations surveyed, 10.6% transported heifers 50 miles or more. Stress from transportation and handling in transit from the heifer grower to the milking herd should be minimized. The impact of shipping stress on late term primiparous cows has not been investigated.

Italian workers investigated the effects of shipping stress on immune function in 6 month old calves (Riondato et al., 2008). Highest leucocyte and neutrophil counts associated with increased concentrations of cortisol and catecholamines, indicated that stress was maximal upon arrival when compared with that before departure, 24 h, and 1 week after arrival (Riondato et al., 2007). Transportation is considered to be one of the main causes of stress in calves (Momede et al., 1982). Biological systems activated in response to stress are the hypothalamo-pituitary-adrenal (HPA) axis, responsible for active responses associated with neurogenic stress, such as transportation, and the sympatho-adrenal medullary system, responsible for passive responses associated with perceived environmental stress such as noise (Mitchell et al., 1988; Griffin, 1989; Minton, 1994).

Hartman et al. (1976) showed that shipping altered the capability of calves to synthesize antibodies. Effects of prepartum shipping on antibody production in colostrum have not yet been investigated. Some heifers are calved and then shipped to the milking facility. Research has not been conducted to evaluate the effect of transportation stress on cattle after calving compared with those with a dry period and that calve on-site.

Norwegian researchers evaluated feeding and proper free stall use by heifers transferred from heifer growers back to the milking herds. On day 2 after transfer, 34% of the heifers refused to use free stalls and by day 15 there will still 23% of the heifers exhibiting this behavior (Kjoestad and Myren, 2001). Refusal to use stalls was significantly associated with rearing accommodations and free-stall layout indicating the importance of previous experience and proper facility design.

Reducing udder edema in primiparous cows

Udder edema is a periparturient disorder characterized by excessive accumulation of fluids in the intercellular tissue spaces of the mammary gland. Udder edema in primiparous cows is a chronic problem in some herds. Udder edema begins several weeks prior to calving and seems to be more prevalent in primiparous than multiparous cows. Challenges with udder edema have been attributed to genetic predisposition, feeding excessive grain, and mineral imbalances (excessive sodium and potassium intake) (NRC, 2001). Prepartum nutrition strategies such as selecting forages low in potassium and reducing sodium intake may help reduce the incidence of udder edema.

Research at the University of Florida conducted a retrospective observational study to evaluate risk factors for udder edema in primaprous cows calving with and without udder edema (Melendez et al., 2006). First test day DHIA milk yield was lower in cows that developed udder edema (3.6 kg/day) than in normal cows and cows with udder edema were 1.62 times more likely to develop udder edema in the second lactation (Melendez et al., 2006). These data suggest that dry period feeding errors that put cows at risk for udder edema must be taken into account. Additionally, first calf heifers with udder edema should receive added attention as they may be at increased risk for other disorders.

Prepartum exercise for primiparous cows?

Exercising close-up heifers has become a standard procedure on some dairy farms in the Midwest. Exercise lots for dry cows have been incorporated into dairy facilities. Additionally, versatile drovers lanes in some facilities allows for ease of animal movement for exercise around the barn. Many producers move first calf heifers through the parlor at milking or when the parlor is not in use to familiarize heifers with the sights and sounds of the parlor and to give them experience with being handled by workers. This experience will become valuable postpartum as these trained heifers will have one less hurdle to contend with.

Summary

We must continue to be vigilant in the quest for improved performance, health and wellbeing of our dairy cattle. Areas where opportunities for improvement exist, such as optimal management of primiparous cows, should not be overlooked. A high degree of variability is inherent in transition cows often shrouding solutions to transition cow failures. Feeding strategies that work for both primiparous and multiparous cows should be considered.